Flexible printed circuit boards have been broadly used. A flexible printed circuit board includes an insulative base film and a conductive pattern that is provided on at least one surface of the base film and that includes a wiring line having a bent portion or a branched portion in plan view.
The flexible printed circuit board may be used while the surfaces thereof are bent at a certain angle, and may be fatigued as a result of repeated changes in the bent state during usage. Accordingly, the bent portion or the branched portion of the conductive pattern may receive a concentrated stress and become disconnected depending on the conditions of use.
For example, Japanese Unexamined Patent Application Publication No. 11-340591 proposes a method for preventing concentration of stress at a crossing portion of wiring lines of a conductive pattern by providing a fillet at a corner of the crossing portion.